UNO Cavity Liner System: Update & R&D Proposal Statusnngroup.physics.sunysb.edu/uno/UNO05-Aussois/talks/UNO...Geotextile Water Wick Shotcrete (5-10 cm) Cavern Wall Cavern wall excavated,

UNO Cavity Liner System:Update & R&D Proposal Status

R. J. Wilson, D. WarnerColorado State University

M. KuchtaColorado School of Mines

April 6, 2005

April 6, 2005 Kuchta/Warner/Wilson 2

Overview

Proposal overviewCavity liner preliminary designLiterature search/SNOLabSurface prep/TSM/membranes/testing etc.Proposal statusSummary

Real work done by Warner & Kuchta


R&D Proposal OverviewThe main goals of proposal:

To provide feedback for cavity designTo determine if “Thin Spray-on Membrane” (TSM) lined cavity for water containment is feasible (and cost effective)

Outline of R&D plan:Determine mechanically acceptable candidate liner system

Mechanical tests of candidate TSM materials Application of candidate liner materials at CSM Experimental Mine and studies of system mechanical properties.

Test of mechanical and chemical properties of candidate materials before and after immersion in DI water and accelerated agingField test candidate liner in DI water cistern at CSM experimental mine


Cavity Liner RequirementsProvide support for cavity walls

Limit and contain fracturing of cavity wall rockLimit damage to equipment/personnel from surface failuresExact bond strength and tensile properties need to be determinedin conjunction with cavity design

Contain a DI water volume of >500kTSeal out external contamination (including radon)Allow contamination only up to the capabilities of “reasonable”water filtration equipmentAllow repeated fill/empty cyclesEnsure liner systems not damaged by long-term exposure to DI waterProvide a reliable seal for 30+ yearsAvoid breaking the bank!


Cavern Wall Water Containment:strawman design

"Veto" volume

Tyvek ReflectiveLayer

Thin Spray-on Membrane (~1cm)

Thin Spray-on Membrane (Rock Seal ~0.5 cm thick)Geotextile Water Wick

Shotcrete (5-10 cm)Cavern Wall

Cavern wall excavated, rock wall stabilized, surface scaledPreliminary layer of geomembrane (Thin Spray-on Membrane, or TSM) appliedRock bolts/cables, steel mesh installedShotcrete applied, large overhangs filled, surface smoothed“Geotextile” layer applied (water wick to sump at detector base)Surface prepared, TSM applied (several layers, alternating colors?)Water volume makes contact with secondary TSMDetector veto volume isolated from membrane by film layerMain detector volume further separated cavern wall by additional film layer


Questions to be addressed by R&D program:

Mine engineering issues Mechanical requirements - Petersen (CAN), Kuchta

What bond strength is required?What tensile strength is required?

Application issues - KuchtaWhat surface treatment of rock is required before application?What are the general and material-specific environmental concerns?

Retention of bond to cavern surfaceWhat will be the impact of water seepage behind barrier?What is the impact of multiple fill-empty cycles ?

Detector engineering issuesHow will we interface with PMT mounting scheme? - Wilkes


… questions (contd.):Detector Engineering Issues (Cont.):

Water containment - WarnerHow many TSM layers needed to ensure water sealWhat is an acceptable water leak rate (can be supported by reasonable water handling system without compromising liner system)?

Extractables/Leachables from liner - WarnerWhat will migrate into the water?How much?Ease of filtration?

Migration of contaminants through barrier - WarnerWhat will penetrate, and how fast?Particular concern – radon

Stability/chemical resistance - WarnerHow will the TSM polymer respond to aggressive DI water?What will the impact of DI water on shotcrete mechanical properties beHow will water vapor permeating the TSM affect the bond to the rock/shotcrete surface?


Literature searchMuch of the available information is empirical, even anecdotal.

Several options exist for both liner mechanical design (number and ordering of layers) and for materials to be used. Custom materials are also an option, particularly for TSM layers

Specific information about water-filled cavities is limited – most material found is from HEP experience! Not much published literature, some internal notes.


Experience at SNOLabDavid Sinclair (SNOLab director) has been very helpful

Not much published data regarding cavity design – Sinclair is looking into securing internal reports/documents for us.UNO straw-man design very similar to SNO design, though arrived at independentlySNO used Urylon for TSM – now “out of favor” due to difficulties with applicationMulti-layer TSM application (alternating colors) necessary to discover pin-prick leaks (initial cistern test leaked badly)Smoothing and preparation of shotcrete surface criticalSNO cavity leaks slowly – believed to be due to penetrations in cavity liner. PMTs should be suspended from top deck


Inner TSM LayerDeparture from traditional wall support structure (shotcrete directly onto rock)May improve

Resistance to external water contaminationBond strength to wallProvide improved wall support (reactive support)

Need to investigate:Material choiceImpact on shotcrete bond strength, overall liner strength and adhesion

Thin Spray-on Menbrane

Cavern Wall


Surface Preparation

Freshly Blasted Rock

After High-Pressure Scaling

Surface preparation is key to liner adhesionOptimal scaling procedure will be determined as part of R&D program

0.00

0.50

1.00

1.50

2.00

2.50

0 10 20 30 40

Water Pressure (MPa)

Bon

d St

reng

th (M

Pa)

Break on bond

Break in shotcrete

Average

Shotcrete bond vs. water jet pressure


In situ Mechanical Testing

a) b) c)

CSM has a teaching mine available to test proposed liner designs.Equipment exists for applying sample TSM/shotcrete liners and testing them.Bond strength and ground support can be measured up to 2.5 MPa.


ShotcreteShotcrete layer (5-10 cm)Main questions

Formulation (e.g. latex stabilizer)Interaction with DI Water -DOE nuclear-storage people worry about calcium leaching from portlandite, leading to reduction in material properties -material strength, Young’s modulus - and stress crackingWill shotcrete benefit from (require?) wire mesh supportBond strength to TSM layer

Shotcrete (~10 cm thick)


Shotcrete being applied


Geotextile layerGeotextile "Water Wick"Acts as “wick” to prevent

accumulation of water behind TSMWater collects in sump at base of wall and is pumped awayTypical material –non-woven polyolefin sheet (e.g. Tyvek)Need to investigate:

DurabilityBond to shotcretePrevent from being center of bacteriological contamination


Liner System Design:Drainage and Geotextiles

Water draining through tubes in shotcrete wall backed by geotextilemembrane Similar drainage layer may be needed behind UNO shotcrete wall depending on water seepage rate


Outer TSM LayerThin Spray-on Membrane

(Detector Water Seal)Outer TSM layer provides primary water containmentPrevents infiltration of environmental contaminants (dissolved ions, radon, etc.)Prevents detector volume leakageMay be custom-formulated for our applicationMust not leach excessive contaminants (plasticizers)Must be long-term stable for DI water exposure


Mechanical Testing

We have access to the materials lab at CSU, which allows us to characterize candidate TSM materials.

Bond strengthModulus of elasticityUltimate strengthElongation at yield

Provides critical input into cavity design.


Accelerated Membrane AgingConstruct a temperature-controlled DI water immersion tank at CSU to allow for accelerated (high temperature) aging of TSM samples

DI water will be tested before and after sample immersion to look for extractables (commercial testing lab)

Mechanical properties of TSM materials will be re-tested following immersion aging


Accelerated Aging in CSM test Mine

A test cistern (~10,000 L, 10 m2 x 1 m deep) can be produced in CSM experimental mine and candidate liner system applied.DI water system from CSU will be used to maintain high-purity, high temperature DI water in cisternTests will be done on cistern leak rate and DI water immersion impact on membrane bond strength to shotcrete and mine wallRepeated water fill/empty cycles can also be tested


Conclusions

R&D Planning for cavity liner systems is well developed - CSU (Warner), CSM (Kuchta) collaborationExamples exist – SNO, KamLAND, but questions remainR&D proposal funds to study new TSM/Shotcrete ground support designs and long-term aging effects of DI water on TSMs and adhesion - ~$210kImportant feedback into cavity design and detector costing.

Documents

UNO Cavity Liner System: Update & R&D Proposal Statusnngroup.physics.sunysb.edu/uno/UNO05-Aussois/talks/UNO...Geotextile Water Wick Shotcrete (5-10 cm) Cavern Wall Cavern wall excavated,